220 Mr. Denham Smith on the 



amethystine red colour as to be apparently opake except at 

 the edges, but by dilution its colour is readily perceived ; it 

 gradually decomposes, evolving oxygen gas and depositing 

 sesquioxide of iron; heat facilitates this decomposition; at 212° 

 F. it is completely effected, and the solution remains colour- 

 less. It is decomposed, evolving oxygen, by sulphuric and 

 nitric acids, chlorine is liberated by the addition of hydro- 

 chloric acid ; by .oxalic acid, carbonic acid gas mixed with 

 oxygen is given off'. It affords no precipitate with the salts of 

 lime, magnesia, or strontian, but on the addition of a barytic 

 salt a voluminous crimson-red precipitate falls, which may be 

 washed, collected and dried at 212° without changing colour. 

 With the metallic salts, the bases of which are capable of 

 combining with more than one equivalent of oxygen, as 

 nickel, manganese, &c, it produces the superoxide of these 

 metals, but with the salts of zinc and metals combining with 

 but one equivalent of oxygen, it precipitates their oxides and 

 evolves oxygen gas. 



When the deep pink-coloured solution is prepared by pass- 

 ing a current of chlorine gas through concentrated solution 

 of potash holding oxide of iron in suspension, or through the 

 deep amethystine solution already described, keeping the ves- 

 sel cool during the passage of the gas, the solution obtained 

 is of a lighter colour than the amethystine liquid and very 

 permanent, it having been kept for months in close vessels 

 without decomposition being completely effected, the gradual 

 progress of which however is shown by the deposition of a 

 light brown substance (sesquioxide of iron ?). This chlori- 

 nated solution may even be evaporated and a pink salt ob- 

 tained, but I have been unable to isolate by any means I have 

 attempted the potash salt of this oxide of iron. I may add, 

 that the characters assigned to these two solutions by the 

 French and German chemists are generally in accordance 

 with my own observations. 



Although foiled in my endeavours to obtain the potash salt 

 free from admixture of other salts, I was yet enabled to de- 

 duce from it the composition of this new oxide of iron, which 

 in accordance with my suggestion, Sept. 1841, is now usually 

 called ferric acid, and subsequently to confirm this consti- 

 tution by the analysis of the barytic salt. 



The mode of analysis was extremely simple, being founded 

 on the perfect decomposition of the deep amethystine solu- 

 tion at 212°. A solution of the reddish-brown fused mass was 

 prepared with ice-cold water and with the precautions before 

 described ; when the insoluble portion had subsided, which it 

 did rapidly, and a portion of the solution had been tested by 



